Effects of wave action on the growth and survival of the scallops Euvola ziczac and Lyropecten nodosus in suspended culture

Abstract

Abstract We examined the impact of wave induced movement on two species of scallops in suspended culture in the Golfo of Cariaco, Venezuela, by comparing growth of juveniles in cages suspended at 6.5 m in depth using two methods. In one case movement from wave action was transmitted to the cages from supporting buoys at the surface, and in the other the supporting buoys were in deeper water, just above the cages, so that the cages were only slightly affected by wave action. For the scallop Euvola ziczac , which is normally found on sandy bottoms, the suspension methods markedly affected growth. After a 31-day growout period, all measured body parameters were markedly smaller for the scallops strongly affected by wave action than for those less exposed to wave action. The differences were 27.0% for muscle mass, 28.7% for digestive gland mass, 24.6% for the mass of remaining somatic tissues, 29.4% for gonadal mass, 13.1% for shell mass and 8.4% for shell height. Survival was 72–75% for the scallops more strongly affected by wave action compared to 94–100% for those less affected by wave action. In contrast, parallel observations on Lyropecten nodosus , which is normally found on rock and coral bottoms, showed no evidence of an effect of wave action on either growth or survival. L. nodosus was probably less affected by wave action than E. ziczac because its movement in the cages was likely reduced by its byssal attachment and by its rugose and more flattened valves. For species such as E. ziczac , wave induced movement of culture enclosures should be minimized either by choosing protected sites or by using techniques that reduce the impact of waves.